The Hebrew word for altar comes from a verb meaning “to slaughter for sacrifice.” Another word translated as “altar” in Ezekiel 43 literally means “mountain of God.”
Before Moses, altars were sometimes built on mountains (see Genesis 12:8). When the Israelites received the law of Moses, they were told there would be only one place where people could make acceptable offerings, though it appears there were also exceptions (see Judges 6:24; 1 Samuel 7:9).
Altars had to be made of unhewn stones—meaning stones not cut with human tools—or of earth (see Exodus 20:24–25).
Worldly scholars have different theories about why various people throughout the ancient world had altars and performed sacrifices, but they have no definitive answers. Through modern revelation, however, we learn that these sacrifices had a common origin with Adam (see Moses 5:5–8). As President Joseph F. Smith (1838–1918) explained:
“Undoubtedly the knowledge of this law [of sacrifice] and of other rites and ceremonies was carried by the posterity of Adam into all lands, and continued with them, more or less pure, to the flood, and through Noah … to those who succeeded him, spreading out into all nations and countries. … What wonder, then, that we should find relics of Christianity, so to speak, among the heathens and nations who know not Christ, and whose histories date back beyond the days of Moses, and even beyond the flood, independent of and apart from the records of the Bible?” (“Discourse,” Deseret News, Feb. 19, 1873, 36).
An altar is:
Raised from the earth. As we draw near to God and kneel humbly before Him, he elevates us. And ancient sacrifices were “a similitude of the sacrifice of the Only Begotten of the Father” (Moses 5:7), who was “lifted up upon the cross, that [He] might draw all men unto [Him]” (3 Nephi 27:14).
Built in a high and holy place. Today, we go to holy places to make our offerings to the Lord. At the temple we participate in exalting ordinances, and at church we partake of the sacrament.
Built for sacrifice. Adam’s sacrifice pointed his mind to Jesus Christ (see Moses 5:5–8). By going to God’s altar, we forsake the world and “offer a sacrifice … of a broken heart and a contrite spirit” (D&C 59:8). We thus “observe [our] covenants” and can be “accepted of [the Lord]” (D&C 97:8).
Where offerings or incense were burned. The smoke from burnt offerings rose into the heavens, representing our dedication to God. The incense represented people’s prayers rising up to God (see Psalm 141:2; Revelation 5:8; 8:3–4).